1. Field of the Invention
The invention relates to an automatic shift control system in which gear positions are established when a selected one or more of friction engagement devices and a one-way clutch are engaged.
2. Description of Related Art
A control system of an automatic transmission which enables the vehicle to run, in the event of a failure to detect an operation position of a shifting member, is well known in the art. One example of this type of control system is a hydraulic control system of an automatic transmission described in Japanese Patent Application Publication No. 2007-177934 (JP 2007-177934 A). When a shift position cannot be detected, control for forming a forward first-speed position is performed, and the forward first-speed position is kept formed as it is if the actual shift position is a forward range, as described in JP 2007-177934 A. When a shift position cannot be detected, and the actual shift position is a reverse range, a forward range pressure needed to form the forward first-speed position is not generated from a manual shift valve that operates in association with the shift lever, and a hydraulic control circuit is configured to supply a reverse range pressure generated from the manual shift valve, to an engagement device for forming a reverse or backward traveling position, as also described in JP 2007-177934 A.